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Short answer
ASTM C476 is the standard specification for grout used in masonry construction. It covers two types, fine grout and coarse grout, and it sits in a chain of standards: C476 defines the grout, ASTM C1019 covers how grout is sampled and compression tested, and ASTM C1093 covers how the testing agency is evaluated.
Definition and scope
ASTM C476-23 is titled “Standard Specification for Grout for Masonry.” The ASTM store describes its scope this way: “This specification covers two types of grout, fine and coarse grout, for use in the construction of masonry structures.” It is maintained by ASTM Committee C15 (Subcommittee C15.30) and published in the Book of Standards, Volume 04.05.
The standard is a material specification. It says what the grout is. It does not describe how a sample is taken from the wall or how a test cylinder is crushed; those jobs belong to other standards, covered below.
Fine grout and coarse grout
The two types differ in aggregate. ASTM states that fine grout is manufactured with fine aggregates, and that coarse grout combines coarse and fine aggregates. The National Ready Mixed Concrete Association (NRMCA) gives size figures in its CIP 22 “Grout” sheet: fine grout uses aggregates smaller than 3/8 inch (9.9 mm), and coarse grout allows aggregate up to 12.5 mm.
CIP 22 says the choice between them “depends primarily on the clear dimensions of the space being filled by the grout.” It also notes that slumps of 8 to 11 inches are generally required for both fine and coarse grout.
| Grout type | Aggregate (ASTM store page) | Size figure (NRMCA CIP 22) |
|---|---|---|
| Fine grout | Made with fine aggregates | Aggregates smaller than 3/8 inch (9.9 mm) |
| Coarse grout | Coarse and fine aggregates combined | Aggregate up to 12.5 mm |
Conventional and self-consolidating grout
The 2023 edition also distinguishes grout by how it is placed. Conventional grout needs mechanical consolidation when placed, by puddling or vibration. Self-consolidating grout does not. This split matters for the next section, because the two are specified differently.
Specified by proportions or by strength
Conventional grout can be specified in one of two ways: by proportions, or by strength requirements. Self-consolidating grout is specified by strength requirements only.
NRMCA CIP 22 explains why the proportion route deserves care. C476 provides prescribed proportions by loose volume that are convenient for small quantities, but these mixes “have high cement contents and tend to produce much higher strengths” than required. CIP 22 also warns that converting loose-volume proportions into batch weights per cubic yard “is subject to errors,” and says that for ready-mixed grout the order should state consistency and compressive strength. It adds that the specified compressive strength must be at least 2000 psi.
| Grout | Consolidation when placed | How it can be specified |
|---|---|---|
| Conventional | Mechanical, by puddling or vibration | Proportions, or strength requirements |
| Self-consolidating | No mechanical consolidation | Strength requirements |
How C476 relates to C1019 and C1093
Three ASTM documents form the chain around masonry grout, and each answers a different question.
- ASTM C476 answers “what is the grout?” (fine or coarse, conventional or self-consolidating, specified by proportions or strength).
- ASTM C1019 answers “how is it sampled and compression tested?” It is maintained by Committee C15.20; see our guide to sampling and testing masonry grout.
- ASTM C1093 answers “who is qualified to do the testing?” It covers the evaluation of testing agencies. For the wider accreditation picture, see ISO/IEC 17025 and A2LA accreditation.
Where it matters for labs and quality staff
A grout strength result only means something against the right specification. C476 separates grout by type (fine or coarse) and by placement (conventional or self-consolidating), and it separates two routes to a compliant mix: prescribed proportions or a strength requirement. NRMCA CIP 22 adds that for ready-mixed grout the order should state consistency and compressive strength, and that the specified compressive strength must be at least 2000 psi. A laboratory reading a strength report for grout therefore needs to know which type and which route the grout was ordered under, since that is what the result is judged against.
Common misunderstandings
- “C476 is the grout test method.” It is not. It is the material specification; compression testing of grout is the subject of C1019.
- “Prescribed proportions guarantee the right strength.” CIP 22 says the prescribed mixes tend to produce much higher strengths than required, and that the strength requirement must still be specified.
- “Fine and coarse grout are interchangeable.” The aggregate differs, and CIP 22 ties the choice to the clear dimensions of the space being filled.
- “Self-consolidating grout follows the same proportion route.” Per ASTM, self-consolidating grout is specified by strength requirements.
FAQ
What does ASTM C476 cover?
It covers two types of grout, fine and coarse, for use in the construction of masonry structures.
What is the difference between fine and coarse grout under C476?
Fine grout is made with fine aggregates; coarse grout combines coarse and fine aggregates.
Is ASTM C476 a test method?
No. It is a specification for the grout itself. Sampling and compression testing are covered by ASTM C1019.
What is the difference between conventional and self-consolidating grout?
Conventional grout needs mechanical consolidation when placed, by puddling or vibration; self-consolidating grout does not. Conventional grout can be specified by proportions or by strength requirements, while self-consolidating grout is specified by strength requirements only.
Sources
- ASTM International, “Standard Specification for Grout for Masonry (ASTM C476-23),” store page: https://store.astm.org/c0476-23.html. Checked 2026-10-29.
- National Ready Mixed Concrete Association, CIP 22 “Grout”: https://www.concreteanswers.org/CIPs/CIP22.htm. Checked 2026-10-29.
- ASTM International, ASTM C1019 and C1093 store pages, as summarized in our ASTM C1019 guide. Checked 2026-10-29.
